1. Field of the Invention
The present invention is generally related to communication plugs and more particularly to communication plugs configured to exhibit reduced levels of modal signal conversion.
2. Description of the Related Art
Conductors that are not physically connected to one another may nonetheless be coupled together electrically and/or magnetically. This creates an undesirable signal in the adjacent conductor referred to as crosstalk.
By placing two elongated conductors (e.g., wires) alongside each other in close proximity (referred to as a “compact pair arrangement”), a common axis can be approximated. If the opposing currents in the conductors are equal, magnetic field “leakage” from the conductors will decrease rapidly as the longitudinal distance along the conductors is increased. If the voltages are also opposite and equal, an electric field primarily concentrated between the conductors will also decrease as the longitudinal distance along the conductors is increased. The compact pair arrangement is often sufficient to avoid crosstalk if other similar pairs of conductors are in close proximity to the first pair of conductors. Twisting the pairs of conductors will tend to negate the residual field couplings and allow closer spacing of adjacent pairs. However, if for some reason the conductors within a pair are spaced far enough apart, undesired coupling and crosstalk may occur.
The structure of many conventional communication connectors (including the RJ-45 type connector) is governed by standards such as FCC part 68 and the TIA/EIA 568 standards. Referring to FIG. 1, a conventional telecommunications connector 10 typically includes a communication plug 20 and a communication jack or outlet 30 configured to receive the plug. The outlet 30 typically provides an access point to a network (not shown), a communications device (not shown), and the like.
As is appreciated by those of ordinary skill in the art, there are two standardized conventions for assigning the wires of the twisted wire pairs to the contacts within the plug and the outlet: T568A and T568B. For all practical purposes, these conventions are identical except that twisted pairs 3 and 2 are interchanged. For illustrative purposes, the T568B convention has been described and illustrated herein.
Each of the plug 20 and the outlet 30 includes a plurality of conductors or contacts. Turning to FIGS. 2 and 3, the plug 20 includes a plurality of conductors or contacts P-T1 to P-T8. Returning to FIG. 1, the outlet 30 includes a plurality of conductors or contacts 32. Within the communication outlet 30, the outlet contacts 32 are positioned in an arrangement corresponding to the arrangement of the plug contacts P-T1 to P-T8 (see FIGS. 2 and 3) in the plug 20. When the plug 20 is received inside the outlet 30, the contacts P-T1 to P-T8 (see FIGS. 2 and 3) of the plug engage correspondingly positioned contacts 32 of the outlet. The plug 20 has a housing 34 with a rearward facing open portion 36 opposite the contacts P-T1 to P-T8 (illustrated in FIGS. 2 and 3).
The communication plug 20 is typically physically connected to one end portion 42 of a communication cable 40, which is inserted inside the plug 20 through the rearward facing open portion 36. Turning to FIG. 3, the cable 40 may be a 4-pair flexible cord, and the plug 20 may be coupled thereto to create a patch cord 50. The cable 40 allows a communications device (not shown) connected thereto to communicate with a network (not shown), a device (not shown), and the like connected to the outlet 30 (see FIG. 1).
A conventional communication cable, such as the cable 40, includes four twisted-wire pairs (also known as “twisted pairs”), which are each physically connected to the plug 20. Following this convention, the contacts P-T1 to P-T8 of the plug 20 are each connected to a different wire (W-1 to W-8) of the four twisted pairs (referred to as “twisted pair 1,” “twisted pair 2,” “twisted pair 3,” and “twisted pair 4” herein). The twisted pair 1 includes wires W-4 and W-5. The twisted pair 2 includes wires W-1 and W-2. The twisted pair 3 includes wires W-3 and W-6. The twisted pair 4 includes wires W-7 and W-8. The twisted pairs 1-4 are housed inside an outer cable sheath 44 typically constructed from an electrically insulating material.
Each of the wires W-1 to W-8 is substantially identical to one another. For the sake of brevity, only the structure of the wire W-1 will be described. Turning to FIG. 4, as is appreciated by those of ordinary skill in the art, the wire W-1 as well as the wires W-2 to W-8 all include an electrical conductor 60 (e.g., a conventional copper wire) surrounded by an outer layer of insulation 70 (e.g., a conventional insulating flexible plastic jacket).
Each of the twisted pairs 1-4 serves as a differential signaling pair wherein signals are transmitted thereupon and expressed as voltage and current differences between the wires of the twisted pair. A twisted pair can be susceptible to electromagnetic sources including another nearby cable of similar construction. Signals received by the twisted pair from such electromagnetic sources external to the cable's jacket are referred to as “alien crosstalk.” The twisted pair can also receive signals from one or more wires of the three other twisted pairs within the cable's jacket, which is referred to as “local crosstalk” or “internal crosstalk.”
The wires W-1 to W-8 of the twisted pairs 1-4 are connected to the plug contacts P-T1 to P-T8, respectively, to form four differential signaling pairs: a first plug pair 1, a second plug pair 2, a third plug pair 3, and a fourth plug pair 4. The twisted pair 2 (i.e., the wires W-1 and W-2) is connected to the adjacent plug contacts P-T1 and P-T2 to form the second plug pair 2. The twisted pair 4 (i.e., wires W-7 and W-8) is connected to the adjacent plug contacts P-T7 and P-T8 to form the plug pair 4. The twisted pair 1 (i.e., wires W-4 and W-5) is connected to the adjacent plug contacts P-T4 and P-T5 to form the plug pair 1. The twisted pair 3 (i.e., wires W-3 and W-6) is connected to the troublesome “split” plug contacts P-T3 and P-T6 to form the “split” plug pair 3. The plug contacts P-T3 and P-T6 flank the plug contacts P-T4 and P-T5 of the plug pair 1. The plug pairs 2 and 4 are located furthest apart from one another and the plug pairs 1 and 3 are positioned between the plug pairs 2 and 4.
A challenge of the structural requisites of conventional communication cabling standards relates to the fact that the two wires W-3 and W-6 of twisted pair 3 are connected to widely spaced plug contacts P-T3 and P-T6, respectively, which straddle the plug contacts P-T4 and P-T5 to which the two wires W-4 and W-5 of the twisted pair 1 are connected. This places the twisted pair 2 and the twisted pair 4 on either side of the twisted pair 3. This arrangement of the plug contacts P-T1 and P-T8 and their associated wiring can cause the signal transmitted on twisted pair 3 to impart different voltages and/or currents onto the twisted pair 2 and the twisted pair 4 effectively causing differential voltages between the composite of both wires W-1 and W-2 of the twisted pair 2 and the composite of both wires W-7 and W-8 of the twisted pair 4 as an undesired cable mode conversion coupling that unfortunately may enhance alien crosstalk elsewhere, which is referred to hereafter as a “modal launch” or “mode conversion.”
In the conventional communication connector 10, the mode of coupling of present concern occurs where the wires W-3 and W-6 of twisted pair 3 are split apart within the plug 20 (i.e., as the wires W-3 and W-6 approach the plug contact P-T3 and P-T6). A significant amount of this type of undesirable coupling also occurs between the plug contacts themselves. This splitting of wires W-3 and W-6 of twisted pair 3, and their associated plug contacts, creates selective capacitive and inductive coupling from the two opposing signals on twisted pair 3, and the increased distance between the wires W-3 and W-6 causes an increase in magnetic coupling between the twisted pair 3 and a first “composite” conductor including the wires W-1 and W-2 (of the twisted pair 2) and a second “composite” conductor including the wires W-7 and W-8 (of the twisted pair 4). In other words, the wires W-1 and W-2 of the twisted pair 2 are treated as a first two-stranded or “composite” wire and the wires W-7 and W-8 of the twisted pair 4 are treated as a second two-stranded or “composite” wire. As a result, a small “coupled” portion of the differential signal originating on twisted pair 3 appears as two opposite common, or “even,” mode signals on the first and second “composite” wires.
Thus, where the first and second “composite” wires are treated equally, the signal transmitted on twisted pair 3 may impart opposite voltages and/or currents onto the twisted pair 2 (i.e., the first “composite” wire) and the twisted pair 4 (i.e., the second “composite” wire), which causes differential voltages between the first and second “composite” wires. Thus there is a “launch,” of an undesired common mode signal that may increase undesired alien crosstalk elsewhere in the transmission system comprising the plug 20, the outlet 30, and their respective cables (e.g., the cable 40).
The transmission path of the plug 20, the outlet 30, and their respective cables (e.g., the cable 40) can be viewed as including the plug 20 in which some of the conductors are located in close proximity to one another and others are spaced farther apart, the interface between a portion of the plug 20 and a portion of the outlet 30, and the outlet 30 wherein conductors are located in close proximity to one another. This conventional arrangement of the transmission path may cause a “modal launch” that extends from the communication connector 10 into the cable 40 connected to the plug 20 and/or other components connected to the outlet 30.
As discussed above, within the plug 20, the modal launch effectively treats the twisted pair 2 as a single two-stranded “paired” conductor (i.e., the first “composite” wire) that is distantly juxtaposed with the twisted pair 4 as its opposite single two-stranded “paired” conductor (i.e., the second “composite” wire). As a result, a “composite” differential pair is created in a communication cable 40 by the wider spaced apart first and second “composite” wires. The wider spacing of the first and second “composite” wires unfortunately enhances vulnerability and sourcing of unwanted crosstalk among other cables situated in the vicinity, such as in a same cable tray, conduit, etc.
The plug-outlet interface is typically the origin of undesired mode conversion coupling in the communication connector 10. At this location, the wires of the twisted pair 3, the plug contacts P-T3 and P-T6, and the outlet contacts corresponding to the plug contacts P-T3 and P-T6 are spaced apart from one another, and may couple (capacitively and/or inductively) with the other conductors of the communication connector 10. One approach to addressing this capacitive and inductive coupling is to cross the split conductors at the plug-outlet interface, ideally at a location near a midpoint of the plug-outlet interface from which mode conversion coupling occurs. For example, the split conductors may be crossed within the communication outlet 30, the communication plug 20, or both. This approach positions a portion of the wire W-3 adjacent to the twisted pair 4 (i.e., the second “composite” wire) and both capacitively and inductively couples the wire W-3 with the second “composite” wire. At the same time, a portion of the wire W-6 is positioned adjacent to the twisted pair 2 (i.e., the first “composite” wire) to thereby capacitively and inductively couple the wire W-6 with the first “composite” wire.
Unfortunately, this approach can present some drawbacks. In the plug 20, the positioning of the wires W-1 to W-8 as described above may cause certain aspects of the transmission performance of the plug to be noncompliant with the TIA/EIA 568 standards. And, in the outlet 30, crossing the conductors can be physically difficult to implement and may compromise mechanical performance.
Thus, a need exists for communication plugs configured to reduce crosstalk. A plug configured to reduce crosstalk that is compliant with applicable communication plug standards is desirable. A further need exists for a communication connector configured to reduce crosstalk caused by unwanted inter-modal coupling between the conducting elements of the connector. The present application provides these and other advantages as will be apparent from the following detailed description and accompanying figures.